A process for reproducibly and reliably realizing thin-layer patterning having details with dimensions of 100 nm or even less is described. This process has been called mold lithography. It is a two-step process : First, a photopolymerization-replication step is carried out? after which pattern transfer is realized through, e.g., wet or dry etching into the substrate material. We performed a number of elementary experiments to evaluate this process. Processing conditions are given and the obtained results are discussed. The strengths of this process are its simplicity and low cost while maintaining compatibility with (standard) semiconductor-technology processing.